


The Newest Addition

by emn_01



Category: Shingeki no Kyojin | Attack on Titan
Genre: Angst, Bisexual Levi (Shingeki no Kyojin), Bottom Armin Arlert, Emotional Eren Yeager, Emotional Hurt/Comfort, FEMININE ARMIN, Fluff, Foursome - M/M/M/M, Gay Eren Yeager, Gay Erwin Smith, Loneliness, Mental Health Issues, Other, Other Additional Tags to Be Added, Polyamory, Smut, Swearing, Switch Eren Yeager, Switch Levi (Shingeki no Kyojin), Top Erwin Smith
Language: English
Status: In-Progress
Published: 2019-02-09
Updated: 2019-06-12
Packaged: 2019-10-24 21:00:46
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 5,098
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17711501
Author URL: https://archiveofourown.org/users/emn_01/pseuds/emn_01
Summary: Worried about their boyfriend's mental health, Levi and Erwin decide to try something incredibly risky in an attempt to help him.





	1. Chapter 1

Quiet music sounded through the kitchen along with the soft humming flowing from a certain brunette's vocal cords. His hips swayed slightly to the beat as his hand used the wooden spoon to stir the beef stew he was currently whipping up. Eren didn't like to toot his own horn, but Jesus did this dish smell good. He's already stolen many tastes, sometimes adding a pinch of salt or another spice, but mostly just tasting to eat it. He was almost sad that he had to share it, for if he weren't so nice, the entire pot would have been emptied into his stomach by now. A loud 'ding' went off behind him, causing him to jump slightly. He rushed over to the oven, mittens now equipped, and quickly pulled the large potato rolls out, the heat immediately hitting his face. After placing them on the cooling rack, he raced over to the prepared melted butter, grabbing a brush and smothered each roll in a generous amount of golden deliciousness.  

Just as he covered the final roll, the slam of the front door entered his ears. His head whipped to the side, only to see a short, pale but no less attractive man shuffle into his kitchen, arms filled with plastic bags. The man's usual scowl was trained on Eren, but he knew the look didn't hold any malice. Levi's face was just unfortunately stuck that way, usually causing strangers to run off. 

"Oh, you two went to the store?" Eren went to grab a few bags from Levi, only for him to turn away from him.

"I've got it, brat. You keep doing whatever." The monotone voice caused Eren to roll his eyes, but he listened nonetheless. "It's Friday, so yeah." Levi placed the bags on the counter, rummaging through them before pulling out random items to later put away. He never let anyone else organize the groceries. Apparently, Levi was the only one who was 'capable' of doing it correctly.

Eren raised an eyebrow as he went back to stirring his stew. "What's Friday got to do with anything?" 

A pair of strong arms suddenly wrapped around his waist, once again causing him to jump in surprise. Someone's nose buried itself into his neck, causing his cheeks to immediately turn red. "Because our little housewife raids the kitchen every Friday to make a goddamn feast." 

"You scared me, Erwin." Eren turned his face to give the skyscraper of a man a peck on the cheek, but Erwin was quick on the draw and stole a quick lip kiss. Eren giggled as his blush intensified. Erwin's grip tightened as he continued to bury his nose into Eren's skin, inhaling his scent deeply. 

"Ew, get a fucking room." Levi walked past the pair, most likely heading to the master bathroom for a quick shower. He managed to peck Eren's cheek on the way, but only lovingly flipped Erwin off as his short frame disappeared into the living room. Levi had always been the least romantic out of the three of them, but that didn't bother Eren in the slightest. 

Eren has been with Erwin and Levi for two years now, them celebrating their second anniversary just last week. He'll admit that at first, he didn't think this relationship would go this far, for their relationship wasn't always so loving. Eren entered the married couples lives as a 'roommate' (or a glorified prostitute if you ask him). Eren was an eighteen-year-old who got kicked out of his house and Erwin and Levi were a married couple who really needed some counseling. They offered him a place to live in exchange for 'spicing up their lives'. One thing led to another and now their here, Eren dating the older men and not planning on leaving anytime soon. 

He was lucky, extremely lucky, to have them in his life. Someone capable of loving him wasn't even an idea in his mind until he met the pair. They always took care of him, making sure to check up on him constantly to make sure he was happy. There was always an endless supply of cuddling the pair offered him and they somehow found a way to always include him in all their activities. Not to mention, the sex was incredible. 

As a horny 18-year-old who didn't know many homosexual men, Erwin and Levi were practically his gods. They opened his eyes to an entirely new different world of pleasure and gratification that he didn't even think possible. But now, as their twenty-year-old boyfriend, the love-making somehow got even better. Perhaps because now there are more sweet whispers in his ears while he's being pounded or the fact that they now both hold him lovingly in their arms after the deed is done. Who knows? It's not like he's going to complain about it. 

~

Twenty minutes later and the three men were situated at the table. Levi, now dressed in his pajamas rather than the uncomfortable suit he was wearing, slowly ate his food, sometimes glancing over at Erwin who was very sloppily slurping his stew down, acting as if he hadn't eaten for days. The conversation was almost none existent, only consisting of 'thank you' and 'this is delicious'. Even though this didn't happen often, Eren didn't want to say anything. Both of his boyfriends' faces looked absolutely grim, dark circles starting to form under their eyes. Today must've been an awful day.

"So, how was your day, kid?" Levi placed his spoon down, most likely not going to eat until Erwin stopped making his disgusting eating sounds.

"Oh, it was fine I guess. Didn't really do anything but cooked today." Levi simply hummed at his response, eyes shifting toward Erwin again. Something about all of this made Eren nervous. These two were being unnatural this evening. While Levi is usually quiet after getting home from work, he's always fine after taking a good shower and eating. And Erwin hasn't really spoken that much at all. Eren would like to think that it was just because his food was so good that he could only focus on that, but he knew that wasn't true. Levi's constant glances made his suspicions worse.

Eren began to tear at his bread a little. "Did something happen today at the office? You guys seem tired." 

Erwin choked a little on his bite, having to pause and wipe his face with a napkin. "Oh, uh n-no. Same old, same old." There was an awkward silence between them once again, making Eren shift in his chair.

"Well then, this was absolutely delicious, doll. Why don't you go take a shower or something and me and Erwin will clean this up?" Levi stood up, grabbing his bowl and snatching Erwin's away from him, causing Erwin's eyes to widen.

"But you've barely touched your food, Levi." He watched as Levi placed Erwin's bowl into the sink and he placed his down to probably dump back into the pot so he wouldn't waste it. 

"Yeah, I had a big lunch. Can't eat another bite, but trust me, it was good." 

Eren crossed his arms. "I made your lunch. You ate exactly what you eat every other day. Why all of a sudden is a turkey sandwich with a goddamn side of grapes too fucking much?" He was beginning to lose his cool, something he has been trying to control for a while, but with all this silence and nervous looks, he felt that he had the right to be a little upset. He didn't want to admit it, but their behavior was really starting to make him worry.

Levi's eyes widened, but he kept quiet. His mouth frowned a bit as he stared at Eren. Erwin was standing now, making Eren even more anxious. They were mad at him, weren't they?

"J-Just...Did I do something? You two are acting like I did something." Eren was on the verge of tears. Damn his emotions. Why can't he ever be in fucking control?

"No, darling, no." Erwin walked over, hugging Eren from behind. "Me and Levi...we just need to discuss something, okay? We promise you're not in trouble. Please just let us clean up and you go relax." 

Eren gripped Erwin's wrist for a moment, mind racing with a thousand thoughts at once. After a minute, Eren yanked himself from his grip before angrily stomping to the bathroom to take a shower. 

~

What the hell did they have to talk about that didn't include him? They want to break up with him, don't they? He had to have done something wrong. 

Eren was angrily rubbing a towel over his damp hair, tears running down his face as he did so. Looking at himself in the mirror, he couldn't blame Levi and Erwin for wanting to get rid of him. He probably seemed more like a psychotic boyfriend than an actual partner. His mind keeps contradicting itself. Part of him was absolutely livid that his boyfriends were treating him like this, keeping some sort of secret from him. The other half, however, was more pissed at himself than anyone else. Why did he always have to act like this, always jumping to conclusions and breaking down right after? Levi and Erwin didn't deserve to be treated this way. They didn't deserve to have to deal with a fucked up guy who couldn't control his own emotions even if he wanted to. That's the whole reason he stays home all day, can't be trusted to go out in public and not freak out. This is stupid. He was stupid.

Eren walked out of the bathroom, face still wet with tears, but the rest of his body relatively dry. He needed to go apologize to his lovers. There was no reason for him to act that way. There could be a hundred different things they needed to discuss without him that doesn't involve them leaving him. 

He made his way into the kitchen only to find his boyfriends not there. The dishes were no longer in the sink, so that makes sense he supposed. But he just walked past the living room and bedroom, so where else could they be? Eren decided to take his body upstairs. It wouldn't make any sense but maybe they were in Erwin's office for whatever reason or even the guest room? Whatever, couldn't hurt to check. 

Walking to the door of Erwin's office, he heard familiar voices coming from inside. Yep, they were in there. Lifting his hand to gently knock on the door, his curiosity got the better of him. What exactly was so important that he had to be left out of it, hm? He leaned his ear against the eavesdropping and probably being very untrustworthy right now, but he had to know what was going on.

"We've got to talk to him about this soon, Levi. It's killing me to do this to both of them." Erwin's voice sounded exhausted. 

"How do you think I feel? I've always gotta be the bad guy when it comes to, Eren. I'm worried about the way he'll react."

"Oh, please. You already know how he's going to react. All we can do is reassure him and let him know that we still love him exactly the same."

It became quiet for a moment, Eren's breath hitching. What's going on? Why are they scared of how'll he react?

"Erwin..." Levi's voice was quiet. "He was doing so well, babe. What if this sets Eren back? You saw him tonight. We made him cry and we haven't even told him yet."

"I think this will be better for him-"

"Yeah well, what if it isn't, huh? What if we lose him over this?" Levi's usually monotone voice was shakey. Shattered breathes could be heard from the other side of the door. Was Levi crying? Levi, his strong, fearless rock was crying. Jesus fucking Christ, what the hell was going on?

"It's going to work out, love. I promise you that I'll make sure we stay together. It might take some time but I think he'll see that we're not only doing this for us but for him, as well."

Levi sniffled. "You promise?"

"Yes, I promise."

"Good. Because the little mouse is hanging outside the door as we speak."


	2. Chapter 2

**Notes for the Chapter:**

> A very short chapter but a chapter nonetheless. I hope you enjoy! Don't forget to leave comments and tell me what you think. Constructive criticism is very much welcomed.

Eren's breath caught itself in his throat. His body froze as his eyes widened at the sound of Levi's voice. Footsteps sounded from behind the door, and before Eren could even realize that he should probably attempt to run away, the portal is swung open, causing him to fall over and land on his knees. He looked up to see a surprised Erwin staring down at him. Levi stood behind him, arms crossed and foot tapping. His face was dry, but his silver eyes were tinted red, the only evidence that the scary man ever broke down. 

They said nothing for a bit, Eren remaining on the ground awkwardly. After a while, Levi breathed heavily out of his nose, fingers pinching its bridge. "Eren, what made you think you wouldn't get caught? You breathe heavier than the average American walking up a flight of stairs." 

Eren stayed silent, glancing back and forth between his two boyfriends. This whole eavesdropping thing was admittedly a bad idea, what with Levi's military strength senses. Eren could never sneak around without Levi noticing something was off. What made him think today would be the one day he could be a successful spy? 

A large hand was suddenly dropped in front of him. He looked up to see Erwin offering his hand to him, face now much more sullen than before. "Come on, darling. I'd prefer you sitting in a chair than on the ground for this." 

Eren reluctantly took the hand, trembling slightly as he stood up. They were going to tell him what's been going on, weren't they? A part of him was relieved that he would finally be let in on this major secret his two loves have been hiding from him. The other part, however, was terrified. As he sat down, he wrapped his arms around his body, noticing that he was shaking slightly. Was he ready to hear this? In reality, he's only realized that Levi and Erwin were keeping something from him today, but in the few hours that this revelation has taken place, Levi has broken down in tears, something he didn't even think possible. If his resistant ex-soldier boyfriend who's only fear his germs finally caved in from this private affair, then was crybaby Eren ready to hear it?

Levi looked over to Erwin, reaching for his hand silently. They stared at each other, almost as if they were daring each other to spit out the first few words. Eren fidgeted in his chair, hand retreating to play with his long hair as the two older men battled wordlessly over who would break the news to him. After what felt like an eternity, Erwin sighed in defeat, turning his face finally toward Eren. 

"Darling...You know we love you, right?" Erwin's eyes seemed clouded, causing Eren to only grow more uncomfortable. When he didn't continue, Eren nodded, begging him to continue. "Well, it's just that...y'know." 

"We're worried about you, Eren." Levi decided to cut in, Erwin giving a sigh of relief. He was always bad at situations like this. "While we're at work, you're here alone all day. That can't be good for your health, doll. It doesn't help that the only company you're getting is from two old men who are boring as shit." 

Eren rolled his eyes at this comment. "For the hundredth time, Levi, you guys aren't boring. Plus, who cares about the age gap? It doesn't make THAT big of a difference." Eren crossed his arms, features turned into an upset pout.

"Eren, when you were born, Erwin and I were literally seniors in high school. You're a young man in a new world and personally, I have no idea what you're talking about half of the fucking time. But that's beside the point." Levi began to rub his temple. "Anyway, what I'm trying to say is that our relationship is pretty fucking strange, you've got to admit it."

"BUT we still love it all the same." Erwin quickly interjected. 

"Oh my God! Just get to the point!" The suspense was killing him. Just what is it that they need to say?

Levi let out a shaky breath, taking one last glance at Erwin before untangling his fingers from his. He moved to Eren, kneeling in front of him before gripping his hands tightly. "We've had a conversation with your therapist. She says that your mood swings are improving, which we agreed with. However, she's saying that your depression is starting to look worse."

Eren didn't agree or deny that claim, only staring deep into Levi's grey orbs. "She thinks it has something to do with our relationship-"

"That's not true! I want a new therapist! This one doesn't know what she's talking about!" Tears began to prick at the edge of teal eyes, a sniffle emerging from the young man. Fuck Dr. Hange. She doesn't know anything! 

"Darling, just listen." Erwin was at this side now, hand rubbing his shoulder soothingly. "We've known Hange for years and she deals with couples like us all the time."

"W-Well, maybe she should find a new job because she sucks at this one! She's trying to break us up!" Eren leaned forward and wrapped his arms as tightly around Levi as possible, breaking down into loud sobs.

Erwin was now rubbing his back, shushing quietly. "No, no darling. She's trying to do the opposite, actually."

"Trust me, kid, we're not going anywhere any time soon." Levi kissed his temple, but the tears didn't stop coming. He didn't believe them. Hange was trying to ruin things, wasn't she? Hange probably hated him for one reason or another. She wanted to get rid of him, huh? He bets Levi and Erwin are tired of him too-

"Listen, doll. We're not sure if her plan is going to work, but she says it's been successful for most of her patients." Levi's voice interrupted his thoughts. He leaned back slightly to look at Levi. His mouth formed a little smile, making Eren feel sick. That was Levi's nervous smile. Something bad's going to happen.

Levi's eyes traveled up to Erwin, silently asking him to join them on the ground. Erwin obliged quickly, bending down from his gigantic height to wrap both him and Eren in his arms. "Hange thinks we should try adding a fourth partner, someone closer to your age."

If Eren could turn around, he'd punch Erwin right in his jaw for uttering such words. "And why in the fuck would we do that?" His voice was raised a bit. He tried to push his way out of their grip, only to be unsuccessful. "So this is some joke to you, huh?"

"What are you talking about?" Levi's voice sounded. Eren finally managed to wiggle out of their grasps.

"You can just 'fall in love' with anyone, can't ya? I fucking knew it. I fucking knew it!" Eren began to breathe heavily. "You don't love me. You're probably bored of me, aren't ya? That's why you want another whore to fuck?"

"No, Eren, what the hell!" Levi raised his voice at him, fist clenching as his patience began to thin. "Of course we fucking love you, haven't we proven that time and time again? Do you think this is any easier on us? We're happy with you, okay? We only need you, but you might need more than just us." His voice cracked at that last sentence. He turned away from Eren, hand now covering his face as tears began to fall. Eren stayed quiet.

The dark office was quiet except for Levi's almost inaudible cries. "We just can't provide everything you need Eren. Is that what you want to hear, huh? We're just two old bastards who can't make you happy."

"L-Levi, I-"

"No, I can't deal with this shit right now." He mumbled before pushing past Erwin and him, exiting through the open office door.

Eren pulled at the stray hairs falling from his ponytail, glancing over at Erwin. The tall man was still, staring at the door that Levi just left through. 

"There's a nice young man who sometimes sits at the same coffee shop me and Levi go to on our breaks. We want you to meet him soon. I think you two will get along." The sound of footsteps hit Eren's ears, quickly fading away, signaling that he was now left alone in the office. 


	3. Chapter 3

**Notes for the Chapter:**

> Sorry for the long wait but I'm back now! Have this short chapter

"Dang it." The boy mumbled as yet another street light flashed a red hand at him, prompting him to stop his footsteps and let the driver's speed by. He waited impatiently, already worried about the time limit he was given to somehow make it to his destination. Armin absolutely despised being late to anything whether that be a dentist appointment or even a birthday party. Being on time always gave the impression that he cared about the other person's time as well as his, or at least he thought of it like that. And unfortunately, this little 'meeting' was something incredibly important to him, and he wasn't sure if he could forgive himself for being late.

He even planned to leave early, his hair already done and outfit already decided. But, as he was about to leave his house, his cellphone rang. A very distressed Connie was on the other side of the line, BEGGING Armin to come over real quick to look over his and his girlfriend, Sasha's, essays. Said girl could be heard in the background frantically sobbing yelling something along the lines of 'We're doomed!' He asked if it could wait till tonight, but like how it usually goes with their homework, it was actually due later that night. With a quick glance at his light pink watch, Armin let out a soft sigh before mumbling a quiet 'I'm coming.' And now, of course, he was about to be late to the single event he had been waiting for the entire week.

Today was the day he was going to meet Levi and Erwin's boyfriend.

Armin had been talking to Levi and Erwin for about two months now, and let's just say he was very confused yet intrigued by this new found 'quirk' he'll call it. He's had boyfriends before, nothing that turned out to be serious or would lead anywhere. In fact, the little blond was still a virgin, much to his dismay. It's not that he was unwilling to try it, it's just that he personally believed you should only do such things with someone you really trusted, and those 'boyfriends' of his never lived up to his standards. Most of them were simply bicurious men who thought it would be okay to experiment with Armin because of how feminine he was. 'It won't be too different than dating a girl, right?' That line always made him seem to boil.

Armin pretty much gave up on his search for love when he hit nineteen, coming to terms with his cat-lady destined life. That was until he was approached by two intimidating men at Wall Rose Cafe, the coffee shop he frequented. A very tall, muscular blond and his hilariously shorter yet also well-built companion innocently asked if they could sit with him, and Armin, alone and not wanting to be rude, hesitantly nodded his head. They started simple enough, introducing themselves and asking his name and if he was from around here since they've never seen him before.

"I was born and raised here. You've probably never seen me before because I never go outside." He joked, taking a sip from his latte.

Erwin let out a chuckle eyes traveling over to the short raven sitting next to him. "You sound just like Levi over here."

Grey eyes rolled as Levi crossed his arms. "The sun is overrated all it does is give you cancer and vitamin D, and I can take a pill for the last one. And probably the first one too." Armin couldn't help but laugh, Erwin quickly joining him.

Their conversation drove back to the original topic, the pair asking him all sorts of questions about himself. How old was he? Where did he go to school? What's his major? All questions Armin happily answered, finding a strange comfort with speaking to the two.

This somehow became a routine, them showing up to the cafe at the same time and deciding to visit with each other. He discovered they were a married couple about a week after their initial meeting, the news not surprising him but making him feel a little sad for some reason. He really liked talking with the men and probably wouldn't object going on a date with one of them. But that also raised a problem, because he couldn't pick which one he could feel that way towards. He was genuinely interested in both of them and choosing one over the other somehow felt wrong. So he just accepted Levi and Erwin's friendship and buried his thoughts deep within his brain somewhere. What's the point of possibly ruining a beautiful relationship?

That was until two weeks ago when they both admitted they felt a romantic attraction to him. He was a bit confused, to say the least. They were both married...TO EACH OTHER. Yet, there was no jealousy or sadness in their eyes, just a bright smile on Erwin's face and a small smirk on Levi's.

"Don't do this to me. It's confusing." He mumbled before burying his face into his hands. Probably not the best answer to the situation, but it was the truth.  He spent so much time suppressing his odd and thought to be one-sided feelings just for the couple to throw it back in his face.

"I know it's confusing, Armin, but it's not a lie. You're so smart, calm, and adorable, what we really need to balance out our crazy lives. You're exactly what we've been looking for." Erwin said with his smile still stuck on his face.

That's when they finally told him about Eren.

"Eren is our boyfriend and the absolute light of our lives." Levi took a sip from his tea. "We love him very much but he's got... problems."

Erwin smacked Levi in the arm. "Don't say it like that! You're making him sound like he's crazy or something." The raven shrugged as he continued to sip on his cup. Erwin sighed. "He's not healthy mentally is what he meant. We've noticed he's been really down lately and seems lonely."

Armin raised a freshly plucked eyebrow at that. "How can he be lonely if he has two boyfriends?"

"Well, we work a lot." Levi butted in. "We, of course, make time for him and take him on dates and all that shit, but other than that he's home alone most of the time. He's doesn't have any friends and doesn't go to school or have a job so-"

"No offense, love, but you're really not selling him right now." Erwin interrupted.

"He should know what he's getting into, Erwin. That is, IF you agree, Armin."

Armin looked between the two older men. "Agree to what?"

"We really like you, Armin. We want you to meet Eren. If all goes smooth we would love if you would join our family." Erwin's smile somehow grew wider.

"But! It's only if you and Eren get along. Sorry but we're a package deal." Levi's eyes traveled over him nervously but his face remained emotionless.

And of course, he agreed. He had really fallen for the married couple without him noticing it. They just knew how to make him laugh and had such a comforting air around them both. Erwin was intelligent and actually could engage Armin in a conversation without stopping him to ask what the heck he was talking about. He could tell he was kind and caring by the way he treated his husband, always trying to hold his hand and quickly offering to buy him another cup when his tea was gone. 

Levi made Armin feel secure, always shooting him compliments unexpectedly, making Armin blush more than he usually does. Even though his words always sounded a bit condescending due to his tone of voice, the meaning behind those words got him every time.  He also couldn't help but laugh at his terrible jokes and 'friendly' insults. The way he played around with Erwin always gave off the vibe of a newlywed and not someone who's been stuck in a relationship for a decade. He kept that spark between them, even after all these years, and Armin couldn't help but want to be a part of that.

So, of course, he said yes. He wanted to be with the older couple, but to do that he also had to feel the same way about their boyfriend. He was nervous to meet Eren. His optimistic side wanted to say that if Erwin and Levi loved him, then he must be just as amazing as the two men. But there was still a part of him that worried about their description of the man. Eren was apparently mentally ill, though a ray of sunshine when he was stable. What if Eren hated him on impulse, or simply wasn't in the right mindset to make such a big decision of dating a third person. What if-

A green light caught Armin's eye and snapped him out of his thoughts. He quickly made his way across the street, not wanting him being lost in his thoughts the reason he couldn't show up on time. Luckily, the coffee shop was only a couple of buildings down from where he was, him rushing through the other people walking to make the distance shorter. A few strangers gave him dirty looks but he didn't care. He had a minute to make it to the cafe.

He was in such a rush that he barely realized that he practically ran into Wall Rose's Cafe, tripping dramatically over their welcome mat and landing face first onto the tile floor. The sound of familiar chuckling entered his ears. His now red face shot up to see Erwin and Levi sitting in their usual spot, along with a very attractive brunette raising his eyebrow at him.

**Notes for the Chapter:**

> Don't forget to tell me what you guys think in the comments!

**Author's Note:**

> Yeah, so I skipped to the nitty gritty immediately. Poor Eren is a wreck so might as well show you that right from the start.


End file.
